Measurement of the energy response function of a silicon pixel detector readout by a Timepix chip using synchrotron radiation

In view of applications in X-ray spectral computed tomography, we determine the energy response function of a 300 μm thick silicon pixel detector, read out by a Timepix ASIC, for a wide range of energies, by using synchrotron radiation in the range 5-32.5 keV. We employ a simple analytical model of the charge transport in the sensor to fit the data and to parametrize the energy response function. This allows to interpolate the function between the energies at which the measurements were performed and to extrapolate it outside the experimentally accessible range. The response function thus parametrized is used to predict how an incoming X-ray spectrum will be distorted during the detection process in the sensor. The comparison of the calculation with measurements shows good agreement.